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Researchers ID Link Between Heat and Heart Stress

In a summer of blistering weather, heart researchers have yet more bad news: Higher temperatures can increase inflammation in people with pre-existing heart conditions, impairing heart muscle function and potentially triggering heart failure.

Scientists, in one of the first studies of its kind, believe they have identified a pathway by which extreme heat impairs the heart, particularly among those suffering from heart disease.

Heat is the top weather-related cause of death in the United States, and scientists have long known that heat waves increase hospitalization and death rates among susceptible populations — the very young and very old, the poor, and those battling cardiovascular and respiratory diseases, among others. But until now they have not known how heat causes heart failure.

Scientists believe they have identified a pathway by which extreme heat impairs the heart. Credit: pollobarba/flickr.

A study published earlier this year in Environmental Health Perspectives suggests one avenue.

The researchers looked at two key proteins that serve as biomarkers for muscle damage and inflammation in heart failure patients. Researchers found that higher temperatures increased the levels of those proteins 10 to 20 percent, reflecting increased stress on the body in response to inflammation and cell injury. Those responses can lead to heart failure by damaging already weakened heart tissue.

"We're trying to understand more about the pathway and how different factors may influence it," said the study's lead author, Elissa Walker, a researcher at Beth Israel Deaconess Medical Center in Boston. "We're thinking about prevention strategies: We know that weather has these more subtle effects that might lead to heart failure and other, more serious problems."

The study does have its limitations. It surveyed 100 patients in and around Boston who were exposed to a broad temperature range, from 12 degrees to 81 degrees Fahrenheit. But it did not look at how those suffering from cardiac problems would react during the extreme heat or prolonged higher temperatures associated with a heat wave.

"That's really important and we need to be looking at (such scenarios) more closely in the future," Walker said.

The study also looked at only patients with heart failure and systolic dysfunction — problems with the heart's ability to contract and properly pump blood through the body. The findings, researchers cautioned, may not apply to people with other types of cardiovascular disease.

But with more than 27,000 weather records tied or broken so far this year — almost 400 more than in all of 2011, the second-hottest year on record — and more heat and extreme weather expected with climate change, the findings underscore the risk to susceptible populations and the need for those with heart failure risk to avoid the high temperatures that occur in hot summer months.